An electric furnace involving a steelmaking process of melting iron sources such as scrap iron or direct-reduced iron (DRI) using electrical energy and refining the iron sources to targeted components and a target temperature wherein, compared to a converter steelmaking method, initial investment costs are affordable since a blast furnace, a raw material processing system, and a sintering system are not required, and is applicable to the production of special steel or stainless steel for small quantity multi-item production, as well as carbon steel. In addition, the emission of greenhouse gasses such as carbon dioxide is very low during the steelmaking process, about one quarter that of a blast furnace. Furthermore, with the increasing amount of scrap steel available globally, the process is being recognized as a future steel technology in that it is an eco-friendly system that helps to reducing scrap steel.
Increasing oil prices have resulted in increased electricity costs, and this situation has also affected the steelmaking industry using an electric furnace, which has lead to utilizing chemical energy, such as oxygen or natural gas so as to be used as electricity. However, due to limitations thereof, the technical development of reducing power consumption by preheating scraps has occurred.
Preheating scraps is a technique of lowering the amount of power by raising the enthalpy of scraps before the insertion thereof into the electric furnace, which is identical to the technique disclosed in Patent Document 1 below. An integrated preheating electric furnace such as that disclosed in Patent Document 1 is a furnace in which a preheating furnace 2 and a melting furnace 1 are integrated and uses a technique of preheating scrap 3 using waste heat generated in a melting furnace 1 (FIG. 1). However, the entire electric furnace formed integrally with the preheating furnace needs to be tilted in order to decant molten steel 8 produced by an electrode 6 through a tapping port (14). Since the preheating furnace 2 and the melting furnace 1 have to be tilted together, there may be limitations with regard to structural issues and a size of the preheating furnace 2 with respect to tilting.
There is provided another method, as disclosed in Patent Document 2 below, of implementing the vertical preheating furnace 2 and the melting furnace 1 separately. Such an electric furnace is configured so that when charging scrap, the preheating furnace 2 is moved via a transfer part 34 and attached to the melting furnace 1, and when the melting furnace 1 is tilted, the preheating furnace 2 is removed. However, in such a case, a problem does not arise with regard to the volume of the vertical preheating furnace 2, but since the preheating furnace 2 is moved, there is a problem of exhaust gas from the melting furnace 1 being emitted externally or ambient air entering the melting furnace/preheating furnace. Also, although continuous charging of scrap is possible, the issue of a non-conductive period may arise, with the melting furnace 1 having to be tilted by removing a power inserter during tapping, leading to continuous melting operations and flat bath operations being impossible.
On the other hand, generalized methods such as MIDREX or HYL and the like exist, as a method of reducing iron ore and using the reduced iron ore as a steelmaking raw material in an electric furnace. However, since such methods consume a relatively large amount of time in achieving a target reduction rate, the methods are not applicable to a high-productivity electric furnace having a reduced tap-to-tap time in order to raise productivity by linking a reducing furnace with an electric furnace.
In addition, during an exhaust gas treatment process in a general electric furnace, dioxins, environmental substances, may be created during a combustion process by a substance containing a halogen element group component being mixed with scrap. Thus, in order to remove dioxins, the installation of a combustion tower able to remove such substances from exhaust gas by heating the exhaust gas to a temperature of 900° C. or higher is required.
(Patent Document 1) JP1998-310813 A
(Patent Document 2) KR2006-7012733 A